A new generation of diet drugs have faced scrutiny from doctors and patients over safety and costs

Drugmaker Orexigen Therapeutics Inc. filed for bankruptcy protection on Monday and plans to sell itself, after failing to find a profitable market for its weight-loss treatment Contrave.

The move underscores the difficulties the pharmaceutical industry has encountered in finding a safe and effective diet drug in the two decades since a drug that was part of the popular “fen-phen” treatment was pulled from the market because it was causing heart problems in patients.